Camshaft adjuster for an internal combustion engine

ABSTRACT

A camshaft adjuster ( 31 ) for an internal combustion engine, including a drive pinion ( 33 ) that can be connected rotationally fast to a crankshaft, a driven pinion ( 1 ) with an inner gearing ( 5 ) and arranged for rotation relative to the drive pinion ( 33 ) about an axis of rotation ( 37 ) as well as an adapter ( 13 ) that is arranged on an inner circumference ( 3 ) of the driven pinion ( 1 ) and through which the driven pinion ( 1 ) can be connected rotationally fast to a camshaft. For this purpose, the adapter ( 13 ) is fixed via the inner gearing ( 5 ) on the inner circumference ( 3 ) of the driven pinion ( 1 ). A fixing of this type enables manufacturing of a camshaft adjuster ( 31 ) with the lowest possible complexity of fabrication and correspondingly low costs.

FIELD OF THE INVENTION

The invention concerns a camshaft adjuster for an internal combustion engine, comprising a drive pinion that can be connected rotationally fast to a crankshaft, a driven pinion comprising an inner gearing and arranged for rotation relative to said drive pinion about an axis of rotation as well as an adapter that is arranged on an inner circumference of the said driven pinion and through which the driven pinion can be connected rotationally fast to a camshaft.

BACKGROUND

A camshaft adjuster serves for a controlled adjustment of the phase position between a camshaft and a crankshaft in an internal combustion engine and thus enables an optimized setting of valve opening and closing times through the engine load and the speed of rotation of the engine. This enables a clear reduction of fuel consumption and exhaust gas emission as well as an enhancement of the engine performance.

In the course of the development of economic and low-emission internal combustion engines, electro-mechanical camshaft adjusters have also been used as an alternative to hydraulic camshaft adjusters. In the case of electric camshaft adjusters, an electric adjusting motor in driving connection with an adjusting shaft generally serves as a so-called adjusting member. The transmissions used are generally triple shaft transmissions. Driving power originates from a drive pinion mounted on the crankshaft and through a driving shaft, while power take-off is performed through a driven shaft and a driven pinion connected rotationally fast to a camshaft. The adjusting power is transferred by an electric adjusting engine via an adjusting shaft into the triple shaft transmission and effects a rotation of the driven pinion relative to the drive pinion. Through the relative rotation of the two pinions relative to each other, it is possible to adjust the phase position between the crankshaft and the camshaft.

DE 10 2008 019 586 discloses a camshaft adjuster of the pre-cited type as part of a camshaft adjusting device. The camshaft adjusting device, or camshaft adjuster, comprises a drive pinion and a driven pinion that are arranged for rotation relative to each other. For this purpose, the drive pinion is configured as an annulus into which the driven pinion is inserted. The driven pinion is configured on its inner circumference with an internal gearing and with an annular reception section adjoining the inner gearing. The reception section serves to receive and position an adapter through which the driven pinion is connected rotationally fast to a camshaft. This adapter is inserted for this purpose into the driven pinion and welded rotationally fixed within the reception section.

Such a configuration does indeed enable a reliable positioning of the adapter but it also necessitates a complex working of the inner circumference of the driven pinion for creating the required reception section for the adapter.

SUMMARY

It is therefore an object of the invention to provide a better camshaft adjuster than the prior art and to make possible a manufacturing of the camshaft adjuster with less expenditure while assuring its best possible functioning ability.

The above object is achieved according to the invention by providing a camshaft adjuster for an internal combustion engine, which camshaft adjuster comprises a drive pinion that can be connected rotationally fast to a crankshaft, a driven pinion comprising an inner gearing and arranged for rotation relative to said drive pinion about an axis of rotation as well as an adapter that is arranged on the inner circumference of said driven pinion and through which the driven pinion can be connected rotationally fast to a camshaft. According to the invention, the adapter is fixed via the inner gearing on the inner circumference of the driven pinion.

The invention takes into account that, to assure a disturbance-free operation of a camshaft adjuster, a reliable torque transmission between the driving element and the driven element must be guaranteed. In the case of electro-mechanical camshaft adjusters, generally, a drive pinion is mounted on a driven pinion which, in its turn, is connected through an adapter to a camshaft.

The adapter itself is arranged typically inside the driven pinion on the inner circumference of the driven pinion. For this purpose, it has been hitherto necessary to provide a separate reception section on the inner circumference. This is not desirable with a view to the complexity of manufacture and the incurred costs.

The invention recognizes the fact that, surprisingly, these problems can be overcome by fixing the adapter via the inner gearing of the driven pinion on the inner circumference of the driven pinion. In this way, the hitherto required additional working of the inner circumference of the driven pinion for fixing the adapter can be omitted. The adapter can be arranged on the driven pinion without the need of providing a special reception section for this on the inner circumference of the driven pinion.

In other words, in this way, an already present and functionally required feature of the driven pinion, namely the inner gearing on the inner circumference of the driven pinion, can be utilized for the arrangement and fixing of the adapter.

The drive pinion is configured particularly as an annulus and comprises an inner gearing which is configured partially or continuously on its inner circumference. The driving power for the drive pinion originates from the rotationally fast connection to a crankshaft. For this purpose, the drive pinion can be configured, for instance, as a chain pulley and the rotationally fast connection to the crankshaft can be realized through a chain. Alternatively, the driven pinion may also be configured as a belt pulley and thus be driven through a belt drive. The driven pinion is usually arranged on the inner circumference of the drive pinion, in which case, the drive pinion can be mounted on the driven pinion.

The driven pinion is preferably likewise configured as an annulus and comprises an inner gearing. This inner gearing is made in the inner circumference during the manufacturing of the driven pinion with help of a so-called broaching method. For this purpose, a broaching needle with an appropriate contour is drawn or pressed through an already made bore in the driven pinion. The cross-section of the broaching needle corresponds to the contour of the inner gearing to be configured on the inner circumference of the driven pinion by the broaching step. In the installed state, the inner gearing, together with the inner gearing of a driven pinion, can form an adjusting gear which can be operated, for instance, through a spur gear of a shaft transmission. For this purpose, then, only a part of the inner gearing of the driven pinion is available because, in the installed state, the adapter is arranged on the inner circumference of the driven pinion.

For its positioning, the adapter is appropriately configured with an outer diameter that is accordingly matched to the inner diameter of the driven pinion. The adapter is configured, for example, with a circular cross-section. The adapter can be pushed into the driven pinion and fixed therein, so that it comes to bear with its outer circumference against the inner circumference of the driven pinion or against the inner gearing thereof. Alternatively, it is also imaginable to configure the adapter with a counter gearing that meshes with the inner gearing of the driven pinion and thus positions the adapter.

The adapter can be configured, for instance, as a substantially flat end cap. The adapter is preferably configured with a central bore through which a central screw for fixing the individual components of a camshaft adjuster to one another can be inserted. During assembly of the camshaft adjuster, the adapter can be screwed on the front end of the camshaft through the fixture of the central screw in the bore. For a rotationally fast fixing on the camshaft, the adapter may comprise further recesses into which fixing elements configured on a front end of the camshaft can engage.

In an advantageous embodiment of the invention, the adapter is pressed on to the addendum circle of the inner gearing of the driven pinion. Typically, in the case of gearwheels, the diameter of the addendum circle defines the outer diameter of the tooth circle, that is, the diameter that is defined by the tips of the teeth. The pressing-in of the adapter on to the addendum circle enables a simple arrangement of the adapter on the inner circumference of the driven pinion because the reception or press-in section is made available through the already present inner gearing. The press-in diameter of the press-in section for the adapter thus corresponds to the addendum circle diameter of the inner gearing. A further working of the press-in section can be omitted. The outer diameter of the adapter is then approximately as large as the diameter of the addendum circle of the driven pinion.

The connection realized through pressing-in can basically have either a fixed or a movable configuration. The operating forces occurring during the operation of the camshaft adjusting device can be transmitted via the effective surfaces of the connection, that is, the contact points between the tooth tips and the outer circumference of the adapter. Further, by reason of the pressing of the adapter on to the addendum circle of the inner gearing, empty spaces remain between the teeth and the outer circumference of the adapter. These empty teeth spaces can be utilized for lubrication of the gearing.

In a further advantageous embodiment of the invention, the inner gearing is configured axially continuous on the driven pinion. The continuous geometry of the inner gearing enables a simple manufacturing or working-in of the inner gearing on the inner circumference of the driven pinion. Because a separate reception or press-in section for the adapter is not required, an enlarged broaching length for making the inner gearing is obtained on the inner circumference. This guarantees a reliable guidance of the broaching needle used.

In addition, through this configuration, material can be saved in the manufacture of the adapter. Due to the fixing via the inner gearing and the concomitant omission of a separate reception section, the adapter can be made with a smaller outer diameter that corresponds approximately to the addendum circle diameter of the driven pinion, so that the adapter is smaller than hitherto used adapters.

Moreover, due to the continuous configuration of the inner gearing, the bearing area ratio of the inner gearing is enhanced so that, for example, its operating life is longer. Because the inner gearing is configured on the entire inner circumference of the driven pinion, the run-out of the gearwheel is situated in the installed state behind the adapter, on an axial end.

The adapter is preferably welded to the driven pinion so that a reliable connection between these two components results. The adapter and the driven pinion are welded segment-wise, particularly at the contact points between the tooth tips and the outer circumference of the adapter, so that the tooth empty spaces are available for the lubricant even after welding. Particularly suited in the present case is laser welding which, due to a high welding speed, narrower weld seam shape and small thermal deformation, assures the precision required in making the connection between said components.

Appropriately, the adapter is configured as an end cap. Due to the configuration as an end cap, in addition to transmitting torque between a camshaft and a crankshaft in the installed state, the adapter can also close the adjusting gear on the side facing the camshaft in axial direction. The camshaft adjuster is thus protected, for example, from outer influences such as pollutions or also against leakage.

In one advantageous embodiment of the invention, the drive pinion is configured as an annulus and mounted on the driven pinion. Particularly suitable for this purpose is a slide mounting with which the two components moving relative to each other are directly in contact with each other. These components slide on each other against the resistance arising from the sliding friction. The resistance can be reduced, for instance, by the choice of a low-friction material pairing or by lubrication. A slide mounting is obviously particularly suitable because this does not require any additional design space.

Appropriately, the invention also provides a stop component for the camshaft and this component is counter mounted an axial direction on the drive pinion. This stop component is preferably configured as a stop ring comprising a stop surface for a camshaft. The stop surface can be configured, for instance, with a projection with which a recess in the front end face of the camshaft can engage. Alternatively, it is also possible to arrange a stop surface directly on the driven pinion. In any case, this stop surface enables a limitation of an angle of rotation between the drive pinion and the driven pinion which is connected rotationally fast to the camshaft with help of the adapter.

In order to assure a reliable fixing of the components on each other, the stop component and the drive pinion are welded to each other preferably, at least partially, that is particularly in the region of the counter mounting. Through this fixing, the stop component is connected rotationally fast to the drive pinion. Alternatively, for example, even other fixing methods such as staking or screwing are imaginable.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiment of the invention are described more closely in the following with reference to an appended drawing.

FIG. 1 shows a driven pinion in a three-dimensional illustration,

FIG. 2 shows the driven pinion of FIG. 1 in a longitudinal section,

FIG. 3 shows the driven pinion of FIG. 1 comprising an adapter, in a longitudinal section,

FIG. 4 shows a top view of the driven pinion comprising the adapter of FIG. 3,

FIG. 5 shows a detail of the driven pinion comprising the adapter of FIG. 3, and

FIG. 6 shows a camshaft adjuster comprising a drive pinion as well as the driven pinion and the adapter of FIGS. 3 to 5, in a longitudinal section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a driven pinion 1 in a three-dimensional illustration. The driven pinion 1 is configured with a ring-shape in form of an annulus and comprises, on its inner circumference 3, an inner gearing 5. Through this inner gearing 5, an adapter can be fixed on the driven pinion 1 in the assembled state. A detailed description of this is to be found in connection with FIGS. 3 to 6.

The inner gearing 5 is configured both axially continuously on the inner circumference 3 of the driven pinion 1 and also continuously on the entire inner circumference 3. This results in a continuous geometry that enables the inner gearing 5 to be worked in a simple manner by a broaching method into the inner circumference 3 of the driven pinion 1. Because a separate reception section for an adapter is not required, the manufacturing of the inner gearing 5 is facilitated. An enlarged broaching length is produced on the inner circumference 3 and enables a reliable guidance of the broaching needle used in the broaching step.

For making the inner gearing 5 by broaching, a broaching needle with an appropriate contour in drawn through a bore in the driven pinion 1. The broaching needle has a cross-section corresponding to the contour of the inner gearing 5 of the driven pinion 1 that is configured on the inner circumference 3 after broaching.

The inner gearing 5 resulting from broaching comprises a number of teeth 7 adjoining one another along the circumference. The diameter of the addendum circle 11 of the inner gearing 5 is defined by the tips 9 of the teeth 7 extending inwards in radial direction from the driven pinion 1. The teeth 7 extend from the inner circumference 3, all, equally far radially inwards within the driven pinion 1.

FIG. 2 shows the driven pinion of FIG. 1 in a longitudinal section. In this illustration, the axially continuous inner gearing 5, that is, the inner gearing 5 extending over the entire axial width 12 of the driven pinion 1 can be clearly seen. This configuration is possible because no separate reception section for arranging and fixing an adapter is required. Thus, the outer diameter in the region in which an adapter is intended to be fixed, corresponds to the diameter of the addendum circle 11 of the inner gearing 5. A broaching needle used for making the inner gearing 5 is therefore reliably guided over the entire axial width 12 of the driven pinion 1.

FIG. 3 shows the driven pinion 1 with an adapter 13 in a longitudinal section. The adapter 13 is configured as a flat, circular end cap and fixed via the inner gearing 5 on the inner circumference 3 of the driven pinion 1. The outer diameter 14 of the adapter 13 is approximately as large as the diameter of addendum circle 11 of the driven pinion 1.

After broaching of the driven pinion 1, the adapter 13 is pressed in on the addendum circle 11 of the inner gearing 5. The press-in section 15, that is, the section on which the adapter 13 is positioned on the inner circumference 3 of the driven pinion, is made available by the already existing inner gearing 5, so that the diameter of the press-in section 15 for the adapter 13 is equal to the diameter of the addendum circle 11 of the inner gearing 5.

After the pressing-in, the driven pinion 1 and the adapter 13 are welded to each other. Through this welding, these two components are connected rotationally fast to each other. Welding is performed at those points at which the radially inwards extending tips 9 of the teeth 7 contact the outer circumference 14 of the adapter 13. After welding, tooth empty spaces 17 remain between the teeth 7 and the outer circumference of the adapter 13 and can be utilized for lubrication of the inner gearing 5 with hydraulic fluid.

FIG. 4 shows a top view of the driven pinion 1 comprising the adapter 13 of FIG. 3, in which the tooth empty spaces 17 between the teeth 7 and the outer circumference of the adapter 13 can be clearly seen. Due to the omission of a separate press-in section, the adapter 13 itself can be made with an outer diameter that corresponds approximately to the diameter of the addendum circle 11 of the driven pinion 1. In this way, material can be saved in the fabrication of the adapter 13.

A central bore 19 is provided at the center of the adapter 13, and, for assembly, a central screw can be inserted through this central bore 13. The central screw can then be fixed in a thread on the front end of a camshaft. In this way, the adapter 13 can be screwed rotationally fast to a camshaft.

Moreover, the adapter 13 is configured with two through-bores 21, 23 that, in the assembled state, serve for a lubricant supply to the camshaft adjuster or adjusting gear.

FIG. 5 is a view of a detail of the adapter 13 of FIG. 3 welded to the driven member 1. In this detail view, it can be seen that, due to the continuous configuration, the bearing area ratio of the inner gearing 5 is particularly high. Because the inner gearing 5 is configured on the entire inner circumference 3 of the driven pinion 1, the run-out end 25 of the gearwheel is situated in the installed state on an axial end behind the adapter 13 that is pressed in on the addendum circle 11.

FIG. 6 shows a camshaft adjusting device 31 for an internal combustion engine, which device comprises a driven pinion 1 and the adapter 13 of FIGS. 3 to 5 in a longitudinal section. The driven pinion 1 and the adapter 13 having already been described in detail in connection with FIGS. 1 to 5, reference can be made here to this description.

In addition to the driven pinion 1 and the adapter 13, the camshaft adjusting device 31 further comprises a drive pinion 33 which, similar to the driven pinion 1, is also configured as an annulus. The drive pinion 33 is mounted through a slide bearing 35 on the driven pinion 1. These two components are arranged for rotation relative to each other about a common axis of rotation 37.

The driving power for the camshaft adjusting device 31 is produced during operation via the drive pinion 33 and a crankshaft, not shown. For this purpose, the drive pinion 33 is configured as a chain pulley 38 and can be connected through a chain rotationally fast to a crankshaft. The torque is transmitted through an adjusting motor, not shown, to the drive pinion 33 and the driven pinion 1 and, thus also, to the camshaft. In this way, a controlled adjustment of the phase position between the camshaft and the crankshaft is achieved.

The camshaft adjusting device 31 further comprises a stop component 39 configured as a stop ring. The stop component 39 is configured with a stop surface 41 for the camshaft, so that a limitation of the angle of rotation between the drive pinion 33 and the driven pinion 1, which is connected through the adapter 13 rotationally fast to the camshaft, is achieved. The stop component 39 is welded on its axial support surface 43 to the drive pinion 33 and is thus connected rotationally fast to this.

Finally, the individual components of the camshaft adjusting device 31 are fixed on one another with help of a central screw 45 that also extends through the central bore 19 of the adapter 13.

LIST OF REFERENCE NUMERALS

1 Driven pinion

3 Inner circumference

5 Inner gearing

7 Teeth

9 Tooth tips

11 Addendum circle

12 Axial width

13 Adapter

14 Outer circumference

15 Press-in section

17 Tooth empty spaces

19 Central bore

21 Through-bore

23 Through-bore

25 Bearing area ratio

31 Adjusting device

33 Drive pinion

35 Slide bearing

37 Axis of rotation

38 Chain pulley

39 Stop component

41 Support surface

43 Stop surface

45 Central screw 

1. A camshaft adjuster for an internal combustion engine, comprising a drive pinion that can be connected rotationally fast to a crankshaft, a driven pinion comprising an inner gearing and arranged for rotation relative to said drive pinion about an axis of rotation as well as an adapter that is arranged on an inner circumference of the driven pinion and through which the driven pinion can be connected rotationally fast to a camshaft, in that the adapter is fixed via the inner gearing on an inner circumference of the driven pinion.
 2. A camshaft adjuster according to claim 1, wherein the adapter is pressed on an addendum circle of the inner gearing into the driven pinion.
 3. A camshaft adjuster according to claim 1, wherein the inner gearing is configured continuously in an axial direction on the driven pinion.
 4. A camshaft adjuster according to claim 1, wherein the adapter is welded to the driven pinion.
 5. A camshaft adjuster according to claim 1, wherein the adapter is configured as an end cap.
 6. A camshaft adjuster according to claim 1, wherein the drive pinion is configured as an annulus and mounted on the driven pinion.
 7. A camshaft adjuster according to claim 1, wherein the camshaft adjuster comprises a stop component for a camshaft and said stop component is counter mounted on the drive pinion.
 8. A camshaft adjuster according to claim 8, wherein the stop component and the drive pinion are welded at least partially to each other. 